Bollettino SPI Vol. 57 (1)
Published in June 2018
- Cau A. (2018)
The assembly of the avian body plan: a 160-million-year long process
Birds are one of the most successful groups of vertebrates. The origin of birds from their reptilian ancestors is traditionally rooted near the Jurassic “Urvogel” Archaeopteryx, an approach that has contributed in defining the dichotomy between the “reptilian” (pre-Archaeopteryx) and “avian” (post-Archaeopteryx) phases of what is instead a single evolutionary continuum. A great and still ever increasing amount of evidence from the fossil record has filled the gaps between extinct dinosaurs, Mesozoic birds and modern avians, and led to the revision of the misleading dichotomy between pre- and post-Archaeopteryx stages in the evolution of bird biology. Herein, the progressive assembly of the modern avian body plan from the archosaurian ancestral condition is reviewed using a combination of phylogenetic methods. The stem lineage leading to modern birds is described using 38 internodes, which identity a series of progressively less inclusive ancestors of modern birds and their Mesozoic sister taxa. The 160-million-year long assembly of the avian bauplan is subdivided into three main stages on the basis of analyses of skeletal modularity, cladogenetic event timing, divergence rate inference and morphospace occupation. During the first phase (“Huxleyian stage”: Early Triassic to Middle Jurassic), the earliest ancestors of birds acquired postcranial pneumatisation, an obligate bipedal and digitigrade posture, the tridactyl hand and feather-like integument. The second phase (“Ostromian stage”: second half of Jurassic) is characterised by a higher evolutionary rate, the loss of hypercarnivory, the enlargement of the braincase, the dramatic reduction of the caudofemoral module, and the development of true pennaceous feathers. The transition to powered flight was achieved only in the third phase (“Marshian stage”: Cretaceous), with the re-organisation of both forelimb and tail as flight-adapted organs and the full acquisition of the modern bauplan. Restricting the investigation of the avian evolution to some Jurassic paravians or to the lineages crown-ward from Archaeopteryx ignores the evolutionary causes of over 60% of the features that define the avian body. The majority of the key elements forming the third phase are exaptations of novelties that took place under the different ecological and functional regimes of the Huxleyian and Ostromian stages, and cannot be properly interpreted without making reference to their original historical context.
- Delfino M., Candilio F., Carnevale G., Coppa A., Medin T., Pavia M., Rook L., Urciuoli A. & Villa A. (2018)
The early Pleistocene vertebrate fauna of Mulhuli-Amo (Buia area, Danakil Depression, Eritrea)
Mulhuli-Amo is an early Pleistocene locality of the Buia area in the Dandiero Basin (Danakil Depression, Eritrea) already known for the presence of Homo remains and stone tools. Recent surface surveys lead to the retrieval of a rich vertebrate fauna that is here described for the first time in order to contribute to the palaeoenvironmental background to the Homo layers of the basin. The following 14 taxa (two fishes, four reptiles, one bird, and nine mammals) were identified: Clarias (Clarias) sp., ?Cichlidae indet., Crocodylus sp., Pelusios sinuatus, Varanus niloticus, Python gr. P. sebae, Ardeotis kori, Palaeoloxodon cf. P. recki, Ceratotherium simum, Equus cf. E. quagga, Hippopotamus gorgops, Kolpochoerus majus, Bos cf. B. buiaensis, Kobus cf. _K. ellipsiprymnus. With the exception of a fish and the bird that were identified at Mulhuli-Amo for the first time, the whole fauna is fully congruent with the taxa already described for the neighbouring locality of Uadi Aalad and confirms, in agreement with all the other proxies, an early Pleistocene age and the former presence of moist grassed habitats adjacent to persistent water.
- Zoboli D., Pillola G.L. & Palombo M.R. (2018)
The remains of Mammuthus lamarmorai (Major, 1883) housed in the Naturhistorisches Museum of Basel (Switzerland) and the complete “Skeleton-Puzzle”
Mammuthus lamarmorai (Major, 1883) is the only dwarf proboscidean taxon known from the Pleistocene of Sardinia (Italy). The fossil record mainly consists of isolated remains reported from a few localities. The species was, however, created for an incomplete skeleton, the first finding of the taxon, fortuitously discovered at the end of the XIX century during the construction of a railway line crossing aeolian deposits cropping out near Funtana Morimenta (Gonnesa, south-western Sardinia). Since the discovery until the beginning of the XX century, various researchers repeatedly collected elephant bones at the site that they sent to various museums or private collectors. The available bone remains of the Funtana Morimenta elephant are currently housed in three museums (Naturhistorisches Museum of Basel, NMB, in Switzerland; Museo di Storia Naturale e del Territorio of Pisa, MSNT and Museo Sardo di Geologia e Paleontologia D. Lovisato of Cagliari, MDLCA, in Italy). The present paper aims to provide the complete list of the material collected by Forsyth Major during several excavation campaigns and currently housed in the NMB. A comparison of the lists of remains from the three museums allowed the authors to exclude the presence of duplicate elements and to attribute all the remains found at Funtana Morimenta to a single fully mature individual.
- Greco F., Cavalazzi B., Hofmann A. & Hickman-Lewis K. (2018)
3.4 Ga biostructures from the Barberton greenstone belt of South Africa:
new insights into microbial life
Raman spectroscopy is a molecule-specific technique allowing the investigation of the chemical structure of organic and inorganic geological materials. Being a non-destructive and relatively non-invasive analytical procedure, Raman spectroscopy is ideally suited to palaeontology. Raman spectroscopy is herein applied to the study of carbonaceous chert facies of the ~3.4 Ga old Buck Reef Chert of South Africa, which contains some of the oldest well-preserved evidence of early life. Laminated chert typically consists of microbands composed of microcrystalline quartz (chert) and an association of siderite and carbonaceous material (CM) in the form of mat-like laminations, simple carbonaceous grains, vein infills and diffuse CM. Using Raman spectroscopy, the structural characteristics of CM in mat-rich chert were investigated and compared with CM-rich grains from the same unit, which were deposited as layers that bear no evidence for mat construction. All CM retains a structural organisation consistent with the lower greenschist grade regional metamorphic imprint, however, a detailed study of the Raman signal of CM revealed some heterogeneity between different sedimentary facies, indicating the presence of different types of CM. Multiple CM precursors are indicated and may reflect different sources or different alteration chemistries of various microbial metabolic pathways.
- ROMANO M. & FARLOW J. (2018)
Bacteria meet the “titans”: horizontal transfer of symbiotic microbiota
as a possible driving factor of sociality in dinosaurs